Technically, the charger is designed to handle it, but it's not the best practice for long-term battery health.
Here's the deal: The M18 Rapid Charger has a maintenance mode. Once the battery is fully charged, it will stop charging. It won't overcharge it in the traditional sense.
However, for optimal battery lifespan:
- Store batteries in a cool, dry place, away from the charger. The ideal storage temperature is between 40°F and 105°F.
- If you store them on the charger long-term, you're keeping them at a higher ambient temperature and a 100% state of charge, which can slightly accelerate capacity loss over years.
If that didn't address your concern, note that the charger itself should be kept in an environment between 40°F and 105°F. Don't leave it in a freezing shed or a hot car.
Heads up: Always recycle old or damaged lithium-ion batteries properly. Don't throw them in the trash.